When thawing and storing fish in a frozen state, significant histological changes occur from ice crystals. Denaturation of some of the muscle proteins also occurs, as a result of which, when thawing the fish, its structure is restored with difficulty and not completely.
Fish is thawed so that its nutritional value does not decrease. Technologists warn against placing frozen fish in warm or hot water. It will begin to lose not only muscle juice, but also minerals, and also absorb water (the weight of the fish will increase by 5-10%), the fibers will begin to stretch.
To thaw the fish, it is immersed in cold salted water (10 g of salt per 1 l of water). The thawing time depends on the size of the fish and varies from 1 to 4 hours. The best way is to thaw fish in cold water with the following condition: 1 kg of fish needs a volume of water equal to 2 liters with one teaspoon of salt dissolved in them.
With this type of thawing, the fish will gradually absorb water and its weight will increase by about 10%. This will be a kind of compensation for the loss of moisture, which is inevitable when the fish is stored in a frozen state. The loss of minerals will replenish the table salt dissolved in water.
Thawing frozen fish can be done in three ways:
1) in air at room temperature, large sturgeon fish are defrosted, placed on tables or shelves and kept for 4 to 10 hours, depending on the size of the fish. Large blocks fish fillets of industrial production are thawed on paper in a cold room during the day to a temperature in the thickness of the layer of -2°C, while the thawed outer layers of the fillet are periodically separated from the block;
2) in water at a temperature of 15°C, small fish are thawed for 2-2.5 hours, large ones - 4-5 hours. An increase in the thawing time leads to a deterioration in the quality of the fish. To reduce the loss of mineral substances, sodium chloride is added to the water at the rate of 7-13 g / l. With this method of thawing, the mass of the fish increases by 5-10% due to the absorption of water;
3) in a combined way thawing of some types of unseparated ocean fish (squam, goby, sardinops, etc.). It is placed in cold water for 30 minutes, then thawed outside to a temperature in the thickness of the muscles of 0°C. Thawed fish is not stored, but is used immediately for cooking.
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